This is cool. There is more info (videos) if you do a search.

A new kind of bridge construction opens and unfolds like an umbrella, creators say. Structural engineers at the TU Wien, or Vienna University of Technology, have built a prototype bridge mechanism with a central umbrella handle and two opposite spokes controlled by a slider. The example bridge spans a river in Austria.

The umbrella method is a completely new way to construct a static final bridge. This TU Wien team first worked on the idea in 2006, and it’s been experimenting and fine tuning since then. Instead of traditional kinds of bridge building—i.e. putting up long-term scaffolding as rebar is laid and concrete is filled into structures—this mechanism is built like a “closed” umbrella and then unfolded into its final position. From there, its hollow girders are filled with concrete and the rest of the structural elements are completed.
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